The function of this core unit is to evaluate the ability of the viral vectors produced by projects of this PPG to transduce human stem cells which have engraftment potential in transplantation models. This will be achieved using transplantations of transduced human hemopoietic cells into SCID/NOD mice. The unit will maintain the SCID/NOD colony and will undertake the transplantations using transduced human hemopoietic cells. The unit will undertake the immunophenotypic typing required to assess the fate of the transplanted cells and will assist the investigators in clonal cultures, in planning the experiments, and in the analysis of the results obtained.